Spatially integrated aerial photography for bridge, structure, and environmental monitoring

ABSTRACT

Spatially Integrated Small-Format Aerial Photography (SFAP is one aspect of the present invention. It is a low-cost solution for bridge surface imaging and is proposed as a remote bridge inspection technique to supplement current bridge visual inspection. Providing top-down views, the airplanes flying at about 1000 ft, can allow visualization of sub-inch (large) cracks and joint openings on bridge decks or highway pavements. On board Global Positioning System is used to help geo-reference images collected and allow automated damage detection. A deck condition rating technique based on large crack detection is used to quantify the condition of the existing bridge decks.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Patent Application No. 61/326,828, filed Apr. 22, 2010, which is hereby incorporated by reference herein in its entirety.

GOVERNMENT SUPPORT

This invention was made with Government support under award number DTOS59-07-H-0005 from the United States Department of Transportation (USDOT). The Government has certain rights in the invention.

BACKGROUND

Currently, the most common practice used to inspect and monitor bridge conditions uses visual inspection reports in which the inspector physically acquires information on the structure at the bridge site. Photos and text-based information are assembled as the inspection is completed and a decision is made regarding the integrity of the structure. However, such technique has been found to be time-consuming, subjective, and rely heavily on personal experiences. The resulting ratings may be inconsistent (Moore et al. 2000).

There are other sensing techniques, such as using NDT (Nondestructive Testing) techniques for evaluation, however, all of these techniques are localized and labor intensive and expensive.

The SI-SFAP is a Commercial Remote Sensing (CRS) technique—CRS technologies, in this case, loosely refer to all airborne/satellite/ground-based non-contact sensing techniques with the exclusion of electromagnetic techniques such as ground penetrating radar, ultrasound and microwaves. Remote sensing techniques are usually employed to address large-scale problems (Hinz and Baumgartner, 2003, Lee and Shinozuka, 2006 and Uddin, 2002). Any technique that collects information remotely can be classified as remote sensing method.

BRIEF SUMMARY OF THE INVENTION

Spatially Integrated Small-Format Aerial Photography (SFAP is one aspect of the present invention. It is a low-cost solution for bridge surface imaging and is proposed as a remote bridge inspection technique to supplement current bridge visual inspection. Providing top-down views, the airplanes flying at about 1000 ft, can allow visualization of sub-inch (large) cracks and joint openings on bridge decks or highway pavements. On board Global Positioning System is used to help geo-reference images collected and allow automated damage detection. A deck condition rating technique based on large crack detection is used to quantify the condition of the existing bridge decks.

The invention is a new process, which is a new use of the existing small format aerial photography. In one example, the invention uses the integration of a GPS system, software, camera and special image evaluation algorithms. The invention can also be used to monitor and inspect building and other structures as well as monitor environmental conditions such as flooding or weather related damage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-5. FIGS. 1-4 show the SI-SFAP (Spatially Integrated Small-Format Aerial Photography) process of the present invention. It is a technical process that uses special aerial photography technique to capture sharp bridge pictures, geo-reference these images and process these images for bridge deck and superstructure deterioration condition indexing.

DETAILED DESCRIPTION AND BEST MODE OF IMPLEMENTATION

The present invention now will be described more fully hereinafter in the following detailed description of the invention, in which some, but not all embodiments of the invention are described. Indeed, this invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well as the singular forms, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and/or groups thereof.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one having ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

In describing the invention, it will be understood that a number of techniques and steps are disclosed. Each of these has individual benefit and each can also be used in conjunction with one or more, or in some cases all, of the other disclosed techniques. Accordingly, for the sake of clarity, this description will refrain from repeating every possible combination of the individual steps in an unnecessary fashion. Nevertheless, the specification and claims should be read with the understanding that such combinations are entirely within the scope of the invention and the claims.

The term “computer” shall mean an electronic device for storing and processing data, typically in binary form, according to instructions given to it in a variable program. A computer may include a desktop computer or a handheld computer such as a laptop, tablet, or smart phone.

In one example of the invention, the SI-SFAP of the present invention is developed as a bridge monitoring technology involving using 1) small airplane, satellite or helicopter, 2) on-board GPS and 3) small format camera (33 mm focal lens), 4) commercial GIS software to geo-reference and stitch the images and 5) use image processing software to quantify crack pattern and identify obstructions and other pertinent information that are associated with bridge and its surrounding conditions. A bridge deck rating algorithm has been devised as a quantifiable indicator for bridge engineers for bridge condition evaluation (described below).

SI-SFAP workflow starts with image capture: The airborne equipment for SI-SFAP involves a low-flying airplane with onboard GPS and high-end digital camera. Several pre-trip flight planning and preparations must be carefully performed: The camera should be prepared by ensuring adequate battery charge and a functional, cleared internal data memory card capable of storing the total number of images identified during the Photo Mission Planning (PMP) phase of work; proper camera lens may require to be installed prior to flight; camera stabilizers may be installed to ensure quality of imagery; the camera may be docked in the underside of the aircraft; GIS software is then used to perform the flight track and photo exposure planning tasks; once the aerial images are being “geo-referenced”, they can be delivered to client or can be used for image processing.

The actual execution of the flight track is dependent on many factors to consider from takeoff to landing including weather and available light, airspace flight restrictions, Estimated Time of Arrival (ETA) at the bridge site. The goal is to minimize shadows on the bridge deck and achieve the correct camera exposure at the time of the bridge flight. Camera settings may need to be adjusted during progress of the flight, to adjust for changes in sun position.

Bridge deck surface cracking is a common phenomenon. However, with the usual ‘wear-and-tear’ due to frequent traffic issues, the cracking can increase in intensity and lead to eventual potholes, scalling, alligator cracking, major transverse cracking, etc. SI-SFAP can be used to quantify cracking, and more importantly, these high-resolution images can also quantify expansion joint openings for possible movement monitoring. The procedure for cracking deterioration analysis includes: 1) extract and label cracks; 2) measure crack size (length and average width). After receiving the core aerial image files, the process for detecting cracks includes a visual scan inspection of the image file by ‘zooming’ onto sections of the bridge surface. Since the images are comprised of pixels, the crack identification is based on pixel color. Detecting possible cracking can also be completed by looking for crack-like features that branch out as the cracking grows compared to normal smoother pixilated surface features. Expansion joints are easily found between spans of the bridge surfaces, unless patching or pavement of the road has covered the joints to the point where straightforward detection is impossible.

After detecting cracking and expansion joints, further analysis can be compiled to determine structural integrity rating. The crack detection is initially a qualitative result determination, but in order to transform this result into quantitative results (Bridge Surface Condition Index (BSCI)).

BSCI rating only considers cracking on bridge surface, and does not differentiate crack types or crack orientations. The BSCI rating process includes: 1) Identify cracks and quantify crack numbers, N, from the aerial images; 2) Determine the area of each span, A, of the bridge structure (based on inspection report or original design); 3) Calculate percentage crack density, D, using Equation 1; 4) Determine deduction value, DV, using FIG. 4.8 (or use Equation 2); and finally, 5) Subtract the highest deduction value to get final rating, BSCI (Equation 3).

The BSCI rating equations, for the aerial photography method, are as follow:

D=N/A  (1)

DV=50×log(D)  (2)

BSCI=100−max(DV)  (3)

where D is crack density, A is individual span area, N is number of cracks per span, and DV is deduction value.

Several applications of SI-SFAP have been identified:

Applications during project planning—for project planning, high resolution aerial photography can be used to assess environmental impact potentials and used as quantitative tools for project estimations. These applications provide sufficient details to allow project managers to establish specific project scopes. Clear photos from SI-SFAP have also been found to be useful in public presentations, since it provides a strong visual for audience, hence, can enhance public relations.

Applications during project construction—frequent SI-SFAP flyovers would provide temporal recordings of construction processes allow project management teams to ensure site safety, optimize operation logistics, reduce traffic flow, minimize construction and environmental impacts, and ensure schedule compliance.

Applications for asset condition assessment and inventory tracking—high resolution aerial photos can help identify defects and damage causes, hence are useful in establishing asset conditions and repair prioritization, which in return, can optimize rehabilitation design and fiscal planning. At times, SI-SFAP can also be deployed for emergency evaluation operations and planning.

Applications during bridge operations—high-resolution imageries can be used to study impacts from surrounding activities near a bridge, including construction blasting and land developments.

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1. A method of inspecting a bridge, the method comprising; a. capturing an image of the bridge using a fixed-wing aircraft, b. geo-referencing the image, c. analyzing the image using a computer. 